if algo != HighwayHash256S {
		return size
	}
	return ceilFrac(size, shardSize)*int64(algo.New().Size()) + size
}

// bitrotVerify a single stream of data.
func bitrotVerify(r io.Reader, wantSize, partSize int64, algo BitrotAlgorithm, want []byte, shardSize int64) error {
	if algo != HighwayHash256S {
		h := algo.New()
		if n, err := io.Copy(h, r); err != nil || n != wantSize {